1. Field of the Invention
The present invention relates to a liquid developer used for wet-type image forming apparatuses based on wet electrophotography, such as copying machine, printer, digital printing machine, and the like.
2. Description of the Related Art
A liquid developer is composed of a toner particle (fine coloring particle) component and an insulating liquid (carrier liquid) component, and the toner particle is usually composed of a resin, a pigment, and a pigment dispersant.
The particle size of toner particles of such a liquid developer is smaller than that of a dry developer, and can be reduced to a size on the order of submicrons, and accordingly reduction of the amount of consumed toner particles can be expected. Regarding the toner particles of the liquid developer, however, a higher content of the pigment relative to that of the dry developer is necessary, and therefore, the pigment dispersant is added. Addition of the pigment dispersant improves compatibility between the pigment and the resin in the toner particle.
For example, Japanese Laid-Open Patent Publication No. 2009-053638 discloses a liquid developer including a pigment dispersant which is an amine compound. Japanese Laid-Open Patent Publication No. 05-333607 also discloses a liquid developer for electrostatic charge development that is composed of toner particles dispersed in the presence of an acid pigment derivative, and an electrically insulating liquid.